Help with engine stall at low rpm!!

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WayneJ

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Good evening everyone I've got a problem that has me down in the dumps. So quick back story, I bought a 94 k1500 with a bad engine, so I bought one with 70k that I've seen run perfect. So I put it in then found out the 4l60e was bad (slipped out of every gear). So I bought the transmission that was attached to the engine I just bought. Now she shifts smooth and has great power. Burns the tires at wot. However when at a stop in any gear except nuetral, or barely on the throttle it will sputter and die. And it's getting worse. Help please. I've switched out throttle bodies and turned the cap until it runs the smoothest I can hear.
 

someotherguy

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What exact vehicle was the engine donor - year and model? It may have the wrong EGR valve. Compare part #'s to the one on your old engine; you may want to swap them.

You also need to...absolutely must...set the timing correctly. Warm it up, disconnect the tan/black wire (behind glovebox or slightly below it on your '94), and set timing for zero. Trying to set these engines by ear is futile.

Richard
 

WayneJ

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It came out of another 94 k1500. I had the timing set exactly how you said with the Pcm timing wire off then connected. But the more I drive it the more it wants to stall he did say something about him having the egr bypassed but still installed. I'm going to check fuel pressure today and re verify timing. The truck also sputters at like 200 or less rpm every time I first start it up for about 10 sec. Then it shoots up to 2k and settles back down. It does it wether the truck is hot or cold.
 

someotherguy

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If the CTS is old, replace it. Use AC Delco or Delphi only.

I'm a little concerned about the comment on the EGR being bypassed.

As far as what RPM's you're seeing, remember the tach starts at 500, not zero.

Richard
 

WayneJ

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Ok so reset the timing today, the truck wouldn't run well with the Pcm disconnected at dead zero. So I set it around 10 and then it ran like a top. So I shut it down connected the pcm and it ran even better. The crappy start up was caused by the map sensor no being connected to the rear of the throttle body. So now it idles perfect.....for about 15 seconds then starts losing rpm and revving up to compensate. And it will do that until it can no longer compensate for the rpm drops and then it dies. I checked fuel pressure out of the pump at the filter and I'm getting 20psi. Any ideas? My alternator took a hit from a poorly thrown hammer and is cracked, could this be the culprit?
 

someotherguy

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Either that 20psi reading is a faulty fuel pressure gauge, or you have the wrong pump in it. TBI small block fuel pressure spec is 9-13 psi, and I don't believe I know of any of the correct pumps able to deadhead anywhere near 20psi. There are pumps for TPI and the 94-95 big block TBI that are 26-32 and look the same, that someone may have incorrectly installed. I would first try a different gauge.

Richard
 

ram1220

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Let me also add that when the EGR went bad on my 90 Sierra 5.7l I had the inconsistent idle also. Engine would act like it wanted to stall and then would rev up. Mine also would set the CEL at highway speeds only. New EGR solved the problem.
 

WayneJ

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I actually replaced my egr last night but to no avail because it still does it. Although it does idle a little smoother until it dies now. I'm going to replace my spark plugs today and my alternator. By replace I mean pull them off the other motor and I'll check back in. I'm genuinely stumped. I'll try again with a new gauge for sure. But isn't the fuel pressure regulator part of the throttle body? And wouldn't it prevent that much psi entering the intake?
 
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